Outlive 25, a remaster of the classic Brazilian sci-fi RTS from 2001, released on Steam
(store.steampowered.com)
In video game terms, I think the 90s can be referred to as a classical period of sorts (at least on PC). 2000 is right at the tail end of the period though.
Vast majority of PC-focused genre were created (or refined in to their current forms) sometime between the tail end of the 80s and the end of the millennium.